The present invention relates to communications systems and methods in which messages are transmitted in the form of wave-guided optical signals.
In switched telecommunications systems, waveguided light is finding use as an information carrier, e.g., for digitally encoded voice, text, and graphics. Systems may be implemented as networks using optical fibers as communications links between communications nodes; alternatively, miniaturized systems or subsystems may utilize substrate-supported waveguides as in so-called integrated optics.
The design of lightwave networks depend critically on the availability of photonic components, e.g., light sources, detectors, couplers, switches, multiplexers, demultiplexers, wavelength filters, optical amplifiers, and other functional elements at network stations and nodes: as the development of such components progresses, new network designs or "architectures" become feasible. A representative selection of network-design disclosures is as follows:
European patent document EP-94-866, published Nov. 23, 1983 in the name of L. d'Auria et al., disclosing a bus architecture with active taps to communications terminals, e.g., a central processor unit, a printer,
U.S. Pat. No. 4,366,565, issued Dec. 28, 1982 to G. J. Herskowitz, disclosing a loop architecture for multiplexing based on the use of a plurality of angular modes in a multi-mode optical fiber;
U.S. Pat. No. 4,470,154, issued Sep. 4, 1984 to T. Yano, disclosing an optical communications network in which switching functions are carried out electrically;
U.S. Pat. No. 4,592,043, issued May 27, 1986 to G. F. Williams, disclosing a wavelength-multiplexed optical communications system in which fiber taps include a tunable resonant cavity for wavelength selection;
U.S. Pat. No. 4,736,463, issued Apr. 5, 1988 to J. D. Chavez, disclosing a fixed, multi-point optical network in a phased-array antenna;
U.S. Pat. No. 4,759,011, issued Jul. 19, 1988 to J. W. Hicks, Jr., disclosing frequency-selective coupling between optical communications loops;
U.S. Pat. No. 8,845,702, issued Jul. 4, 1989 to F. Melindo, disclosing a packet-switching network node with electrical-to-optical and optical-to-electrical signal conversion;
U.S. Pat. No. 4,914,648, issued Apr. 3, 1990 to A. Acampora et al., also disclosing a packet-switched lightwave system with electrical switching at the network nodes;
U.S. Pat. No. 4,922,481, issued May 1, 1990 to J. W. Hicks, disclosing a local-distribution optical communications system including frequency-tunable power taps.
Particularly significant as a motivating factor in network design is the desire to exploit the potentially very large bandwidth available in optical waveguide communications; in current, state-of-the-art systems, such potential is far from realized. Indeed, current systems are limited by an "electronic bottleneck" due to electronic switching functions carried out at network nodes, or by unnecessary power dissipation in (passive) star and bus broadcast designs.
The invention described in the following does not suffer from these drawbacks and offers a network architecture in which purely optical paths are established between selected network users on demand.